Dear EarthTalk: The term "sustainable" seems to be the new green buzzword. What exactly does it mean, particularly when applied to such things, say, as transportation or agriculture?

—Steve Nezhad, Portland, ME

"Sustainable," quite simply, is the positive result of conducting economic, social or environmental activities in such a way that current needs are met without compromising the well-being of future generations. A sustainable activity also does not despoil the here and now, in part because of how it may affect the future.

For example, cars that run on oil and gasoline are unsustainable on both counts: They make use of a non-renewable resource (that is, one that will be completely depleted at some point in the future); and they pollute the environment right now. Thus they negatively impact the present-day as well as tomorrow.

What, then, is sustainable transportation? Any option that moves people or goods while impacting the environment minimally. Walking and bicycling are the most sustainable, using no energy except for leg power and consuming very little or no resources. And public transportation moves large numbers of people at once while also saving space, as one negative impact of cars is that activities tend to spread out through the process of sprawl, creating the need to travel greater distances to obtain goods or get to work.

As such, to a large extent transportation can be made more sustainable through urban design. The closer together we locate shopping and entertainment centers, the easier it is for public transport to get us there, and the less reliant we are on cars. And cars themselves can be more sustainable by running on clean fuels or on technologies, like hybrids, that use less fuel. Better yet, cars of the not-too-distant future will be powered by fuel cells, which run on hydrogen and spew no pollution. Ideally, that hydrogen will be made from water, using power from solar energy, thus creating no pollution at that point in the process, either.

In the realm of farming, sustainable agriculture in its ideal form provides a living for those who farm and supports the local community’s needs while maintaining the natural ecology of the farm and its surrounding environment. According to the National Safety Center (NSC), a "sustainable" farm produces crops without damage to the farm’s ecosystem, including the soil, water supplies and other adjoining resources. Sustainable agriculture is also "intergenerational," says NSC, in that it seeks to pass on to future generations a conserved natural resource instead of one that has been depleted or polluted.

Some examples of sustainable agriculture include avoiding chemicals, rotating crops, and choosing crops that suit the climate, so as to reduce the need for chemicals and preserve the long-term fertility of the soil. In light of modern developments, some might add that avoiding genetically modified crops would also fit with the sustainable model, given the uncertainty of their impact on ecosystems and personal health.

Robert Gilman of the Context Institute defines sustainability as "extending the Golden Rule through timeDo unto future generations as you would have them do unto you." Meanwhile, Paul Hawken of the Natural Capital Institute offers an equally concise summary: "Leave the world better than you found it, take no more than you need, try not to harm life or the environment, make amends if you do."

Dear EarthTalk: In a public restroom, which is the more environmentally sound and healthy option for drying your hands: a paper towel or an electric hand dryer?

—Dee Janis, Binghamton, NY

Most experts would agree that wall-mounted electric hand dryers are preferable to paper towels from an environmental standpoint. Though they do use energy, they shut off automatically and therefore don’t waste energy—and they eliminate the need for paper while also keeping paper out of the waste stream.

But the answer may depend upon whom you ask. World Dryer Corporation, which supplies wall mounted dryers, prepared a study for the Topeka, Kansas public school system, which concluded that switching from paper towels to 102 of its wall-mounted dryers system-wide would save annually 587 trees, 690,000 gallons of water, 34.5 tons of solid waste, 103.5 cubic yards of landfill space, and almost $90,000 per year (including electricity costs), with less than a six-month initial payback period for the cost of installation.

Others are not so quick to give the nod to dryers, and cite sanitation as the reason. The Handwashing For Life Institute (HFL), an association of food service suppliers that includes paper makers, argues that hand dryers have "no place" in restaurant or cafeteria washrooms or in other situations where food is being handled. "Most users walk away with wet hands and wet hands transfer bacteria 500 times more readily than dry hands," says the group’s website. HFL advocates paper towels over dryers because they "remove bacteria from hands and reduce general bacterial counts by an average of 58 percent."

Many hand washers would agree that wall dryers do not work as effectively as paper. After all, who hasn’t given their hands a final swipe across a pant leg after using a hand dryer for a few minutes? California State University facilities manager Gary Homesley was one of those, but in assessing whether or not to replace paper towels with electric dryers at a campus student union, he was shocked to learn of the significant amount of resources used to make paper as well as the large amount of pollutants that paper-making was responsible for discharging into the atmosphere.

Ultimately Homesley chose the Xlerator hand dryer. The manufacturer, Excel Dryers, claims that it will dry hands in 10-15 seconds, and that it addresses the effectiveness issue with a high-velocity air stream that actually blows most of the water off the hands, leaving the thin remaining film of water to evaporate more quickly. The product is the first electric hand dryer to be awarded the Environmental Building News GreenSpec designation for conserving energy and reducing waste, and is also the first to qualify for the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program.

Despite the prevalence of recycled papers and the increased efficiency of electric hand dryers, it may still be disheartening to know that no matter what you are offered at the conclusion of your public restroom visit you are having some environmental impact. For those losing sleep over that, there is always the truly green fallback of carrying your own reusable washcloth.

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